Expansion valve

ABSTRACT

The object of the present invention is to provide an expansion valve that suppresses noise generated when an air conditioner is started, and achieves saving of driving force. The stroke of a valve element is set such that refrigerant flows at a flow rate 1.0 to 1.4 times the flow rate corresponding to the set tonnage. This limits the valve lift of the valve in the fully open state during start-up such that it provides a flow rate of refrigerant only 1.0 to 1.4 times the flow rate corresponding to the set tonnage. This prevents an unnecessary and excessive amount of refrigerant from flowing, whereby it is possible to reduce flow noise of refrigerant during start-up. Further, since the excessive amount of flow of refrigerant is reduced, it is possible to achieve saving of driving force.

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY

[0001] This application claims priority of Japanese Applications No.2002-202013 filed on Jul. 11, 2002, entitled “Expansion Valve” and No.2003-133266 filed on May 12, 2003, entitled “Expansion Valve”.

BACKGROUND OF THE INVENTION

[0002] (1) Field of the Invention

[0003] This invention relates to an expansion valve, and moreparticularly to a thermostatic expansion valve in a refrigeration cycleof an automotive air-conditioning system, for allowing ahigh-temperature and high-pressure liquid refrigerant to expand into alow-temperature and low-pressure refrigerant to supply the refrigerantto an evaporator, and at the same time controlling a flow rate of therefrigerant such that the refrigerant at an outlet of the evaporator isplaced in a predetermined degree of superheat.

[0004] (2) Description of the Related Art

[0005] In the automotive air-conditioning system, a refrigeration cycleis formed in which a high-temperature and high-pressure gaseousrefrigerant compressed by a compressor is condensed in a condenser, andan expansion valve allows the condensed liquid refrigerant to undergoadiabatic expansion to be changed into a low-temperature andlow-pressure refrigerant, which is evaporated in an evaporator, and thenreturned to the compressor. The evaporator to which the low-temperaturerefrigerant is supplied exchanges heat with air in the compartment,thereby performing cooling.

[0006] As the expansion valve, a thermostatic expansion valve is knownwhich senses the pressure and temperature of refrigerant at an outlet ofan evaporator, and controls the flow rate of refrigerant supplied to theevaporator such that the refrigerant is in a predetermined degree ofsuperheat (see e.g. Japanese Unexamined Patent Publication No.2002-310539 (Paragraph Nos. [0034] to [0041], FIG. 6)).

[0007]FIG. 7 is a longitudinal cross-sectional view showing an exampleof the construction of a conventional expansion valve.

[0008] The expansion valve 101 includes a body block 102 having sideportions formed with a refrigerant conduit connection hole 103 forintroducing refrigerant, a refrigerant conduit connection hole 104 fordelivering refrigerant, and refrigerant conduit connection holes 105,106 for being intervened in piping leading from an evaporator to acompressor.

[0009] In a fluid passage between the refrigerant conduit connectionhole 103 and the refrigerant conduit connection hole 104, a valve seat107 is integrally formed with the body block 102, and a ball-shapedvalve element 108 is disposed in a manner opposed to the valve seat 107from the upstream side, and refrigerant undergoes adiabatic expansionwhen it flows through a gap between the valve seat 107 and the valveelement 108. Further, the valve element 108 is urged by a helicalcompression spring 110 via a valve element receiver 109 for receivingthe valve element 108 in a direction of being seated on the valve seat107. The helical compression spring 110 is received by a spring receiver111 and an adjustment screw 112.

[0010] A power element 113 is provided at an upper end of the body block102. The power element 113 comprises an upper housing 114, a lowerhousing 115, a diaphragm 116, and a center disk 117. Atemperature-sensing chamber surrounded with the upper housing 114 andthe diaphragm 116 is filled with refrigerant, and sealed by a metal ball118.

[0011] The upper end of a shaft 119 is in abutment with the center disk117. The shaft 119 is inserted through a through hole 120 formed in thebody block 102, and has a lower end thereof in abutment with the valveelement 108.

[0012] The through hole 120 has an upper part thereof expanded, and an Oring 121 is disposed at a stepped portion thereof, for sealing a gapbetween the shaft 119 and the through hole 120.

[0013] Further, the upper end of the shaft 119 is held by a holder 122which has a hollow cylindrical portion extending downward across a fluidpassage communicating between the refrigerant conduit connection holes105, 106. The lower end of the holder 122 is fitted in the expandedportion of the through hole 120 and retains the O ring 121.

[0014] A coil spring 123 is disposed at the upper end of the holder 122,for suppressing axial vibrations of the shaft 119. The top surface ofthe holder 122 functions as a stopper defining the maximum valve lift ofthe expansion valve 101.

[0015] In the expansion valve 101 constructed as described above, beforethe air conditioner is started, the center disk 117 is in abutment withthe top surface of the holder 122, and the expansion valve 101 is fullyopen. Therefore, when the air conditioner is started, the expansionvalve 101 starts its operation from the fully open state thereof.

[0016] By the way, the automotive air-conditioning system has adifferent required refrigerating capacity depending on the vehicle towhich it is applied, and the capacity demanded of the expansion valve isalso different. The capacity of the expansion valve is expressed intonnage. From the tonnage set depending on the vehicle, the flow rate ofrefrigerant flowing through the expansion valve is determined, andtherefore, the expansion valve is designed such that at least the flowrate corresponding to the set tonnage is guaranteed. In this case, themaximum valve lift is unconditionally set to a sufficiently larger valuethan that corresponding to the set tonnage, for whatever tonnage theexpansion valve may be designed.

[0017] However, the conventional expansion valve is fully open when theair conditioner is started, and the valve lift at that time is largerthan that providing a required flow rate, causing a large amount ofrefrigerant to flow. This increases flow noise generated when therefrigerant passes through the valve, and what is worse, since theexpansion valve is excessively opened, this causes the refrigerant toflow at a superfluous flow rate, resulting in an increase in the drivingforce.

SUMMARY OF THE INVENTION

[0018] The present invention has been made in view of these problems,and an object of the invention is to provide an expansion valve thatsuppresses noise generated during start-up and achieves saving ofdriving force.

[0019] To solve the above problem, the present invention provides anexpansion valve including a power element that senses pressure andtemperature of refrigerant at an outlet of an evaporator and controls avalve lift of a valve portion, to thereby control a flow rate ofrefrigerant supplied to the evaporator, characterized in that a maximumvalue of the valve lift is set such that the flow rate is equal to 1.0to 1.4 times a flow rate of set tonnage.

[0020] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionwhen taken in conjunction with the accompanying drawings whichillustrate preferred embodiments of the present invention by way ofexample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a longitudinal cross-sectional view showing an exampleof the construction of an expansion valve according to the invention.

[0022]FIG. 2 is a diagram showing the relationship between the valvestroke and refrigeration ton.

[0023]FIG. 3 is a diagram showing the relationship between a factor bywhich the refrigerating capacity is increased and noise generated duringstart-up.

[0024]FIG. 4 is a diagram showing changes in noise immediately after theexpansion valve is started.

[0025] FIGS. 5(A) and 5(B) are diagrams for explaining tolerancedispersion, in which FIG. 5(A) illustrates a case of the conventionalexpansion valve, and FIG. 5(B) illustrates a case of the expansion valveaccording to the present invention.

[0026]FIG. 6 is a longitudinal cross-sectional view showing anotherexample of the construction of the expansion valve according to theinvention.

[0027]FIG. 7 is a longitudinal cross-sectional view showing an exampleof the construction of a conventional expansion valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, embodiments of the present invention will now bedescribed in detail with reference to the drawings.

[0029]FIG. 1 is a longitudinal cross-sectional view showing an exampleof the construction of an expansion valve according to the presentinvention.

[0030] The expansion valve 1 according to the present invention has abody block 2 having side portions formed with a refrigerant conduitconnection hole 3 to which is connected a high-pressure refrigerantpiping for receiving a high-temperature and high-pressure refrigerantfrom a receiver/dryer through the piping, a refrigerant conduitconnection hole 4 to which is connected a low-pressure refrigerantpiping for supplying a low-temperature and low-pressure refrigerantexpanded and reduced in pressure by the expansion valve 1 to theevaporator, a refrigerant conduit connection hole 5 connected torefrigerant piping from an evaporator outlet, and a refrigerant conduitconnection hole 6 connected to a refrigerant piping leading to thecompressor.

[0031] Further, in a fluid passage communicating between the refrigerantconduit connection hole 3 and the refrigerant conduit connection hole 4,a valve seat 7 is integrally formed with the body block 2, and aball-shaped valve element 8 is disposed in a manner opposed to the valveseat 7 from the upstream side. Due to this configuration, a gap betweenthe valve seat 7 and the valve element 8 forms a variable orifice forreducing the flow of the high-pressure refrigerant, and thehigh-pressure liquid refrigerant is adiabatically expanded when it flowsthrough the variable orifice. The valve seat 7 is tapered such that theamount of tapering is equal to or more than the amount of axial motion(stroke) of the valve element 8. More specifically, a portion of thevalve hole opposed to the valve element 8 has its edge cut to form atapered hole, and the axial length (height) of the tapered hole is equalto or larger than the length of the stroke of the valve element 8. Here,a smallest-diameter portion of the tapered hole sets the seatingposition of the valve element 8, and even if the valve element 8 ismoved to a farthest position therefrom to make the valve fully open,part of the valve element 8 is positioned within the tapered hole, whichprevents the valve element 8 from moving out of the tapered hole whenthe valve is fully opened.

[0032] Further, in the fluid passage on the side of the refrigerantconduit connection hole 3, there are disposed a valve element receiver 9for receiving the valve element 8, and a helical compression spring 10for urging the valve element 8 via the valve element receiver 9 in thedirection of seating the valve element 8 on the valve seat 7. Thehelical compression spring 10 is received by a spring receiver 11 and anadjustment screw 12 screwed into the body block for adjustment of loadof the helical compression spring 10.

[0033] At an upper end of the body block 2, there is provided a powerelement 13 which comprises an upper housing 14 and a lower housing 15,made of a thick metal, a diaphragm 16 made of a thin metal plate havingflexibility and disposed in a manner dividing the space surrounded withthe housings, and a center disk 17 disposed below the diaphragm 16. Thespace surrounded with the upper housing 14 and the diaphragm 16 forms atemperature-sensing chamber which is filled with two or more kinds ofrefrigerant gas and inert gas, and is sealed with a metal ball 18 byresistance-welding. The center disk 17 has a lower part formed with anincreased diameter such that the part radially protrudes outward, andthe underside thereof is formed to have a flat surface. The inner wallsurface of the lower housing 15 opposed to the underside of a protrudingportion of the center disk 17 is also formed to have a flat surface. Theflat portion of the inner wall surface functions as a stopper limitingthe downward motion of the center disk 17, thereby defining the maximumvalve lift of the expansion valve 1.

[0034] Below the center disk 17, a shaft 19 is disposed for transmittingdisplacement of the diaphragm 16 to the valve element 8. The shaft 19 isinserted through a through hole 20 formed in the body block 2.

[0035] The through hole 20 has an upper part thereof expanded, and an Oring 21 is disposed at a stepped portion thereof. The O ring 21 seals agap between the shaft 19 and the through hole 20, thereby preventingrefrigerant from leaking into the fluid passage between the refrigerantconduit connection holes 5 and 6.

[0036] Further, the upper end of the shaft 19 is held by a holder 22which has a hollow cylindrical portion extending downward across thefluid passage communicating between the refrigerant conduit connectionholes 5, 6. The lower end of the holder 22 is fitted in the expandedportion of the through hole 20 and the lower end surface restricts themotion of the O ring 21 toward the upper open end of the through hole20.

[0037] A coil spring 23 is disposed at the upper end of the holder 22,for urging the shaft 19 from a radial direction. This configuration ofapplying lateral load to the shaft 19 with the coil spring 23 preventsthe axial motion of the shaft 19 from sensitively reacting to changes inpressure of the high-pressure refrigerant in the refrigerant conduitconnection hole 3. That is, the coil spring 23 forms a vibrationsuppressing mechanism for suppressing generation of untoward vibrationnoise caused by vibrations of the shaft 19 in the axial direction.

[0038] Further, the top of the holder 22 has a passage formedtherethrough for communicating the fluid passage communicating betweenthe refrigerant conduit connection holes 5, 6 and the space below thediaphragm 16, and at the same time, the underside of the center disk 17is formed with a plurality of ventilation grooves in a radiallyextending manner, except a central portion with which the shaft 19 is inabutment, thereby allowing the refrigerant returned from the evaporatorto enter the chamber below the diaphragm 16.

[0039] In the expansion valve 1 constructed as described above, beforethe air conditioner is started, the power element 13 detects asufficiently higher temperature than that during operation of the airconditioner, so that the pressure in the temperature-sensing chamber ofthe power element 13 is made higher, which causes the diaphragm 16 to bedisplaced downward as shown in FIG. 1, whereby the center disk 17 abutsagainst the stopper of the lower housing 15. This displacement of thediaphragm 16 is transmitted to the valve element 8 via the shaft 19,thereby making the expansion valve 1 fully open. Therefore, when the airconditioner is started, the expansion valve 1 starts its operation fromthe fully open state, and therefore, the expansion valve 1 suppliesrefrigerant to the evaporator at the maximum flow rate.

[0040] As the temperature of the refrigerant returned from theevaporator is lowered, the temperature in the temperature-sensingchamber of the power element 13 is lowered, whereby the refrigerant gasin the temperature-sensing chamber is condensed on the inner surface ofthe diaphragm 16. This causes pressure in the temperature-sensingchamber to be reduced to displace the diaphragm 16 upward, so that theshaft 19 is pushed by the helical compression spring 10, to move upward.As a result, the valve element 8 is moved toward the valve seat 7,whereby the passage area of the high-pressure liquid refrigerant isreduced to decrease the flow rate of refrigerant sent into theevaporator. Thus, the valve lift of the expansion valve is set to avalue dependent on the cooling load.

[0041]FIG. 2 is a diagram showing the relationship between the stroke ofa valve and refrigeration ton.

[0042] The expansion valve 1 has its capacity determined according tothe refrigerating capacity demanded by the system, and in general, thereare a 1.0-ton type, a 1.5-ton type, and a 2.0-ton type of expansionvalves. In all of these types, the valve element 8 has its valve liftcontrolled within a range of stroke corresponding to the associatedrefrigeration ton. For conventional expansion valves, the maximum valvelift during start-up is set, irrespective of the type, by a certainsufficiently large value of stroke A, e.g. 0.8 mm. However, in theexpansion valve 1 according to the present invention, the maximum valvelift is set by such a stroke as will cause the refrigerant to flow at1.0 to 1.4 times the flow rate corresponding to the designated tonnage.For example, in the case of the 1.0-ton type expansion valve, themaximum stroke is set to a value within a range between a strokeposition B allowing the refrigerant to flow at a flow rate satisfyingthe capacity of 1 ton and a position B′ of the maximum valve liftallowing the refrigerant to flow at 1.4 times the above flow rate.

[0043]FIG. 3 is a diagram showing the relationship between the scalefactor of the refrigerating capacity and noise generated upon start-up,and FIG. 4 is a diagram showing changes in noise immediately after theoperation of the expansion valve is started.

[0044]FIG. 3 shows how the noise generated during start-up of theexpansion valve 1 varies with a change in the scale factor of therefrigerating capacity. According to FIG. 3, noise is steeply increasedwhen the refrigerating capacity is in the vicinity of 1.4 times orexceeds the same. The expansion valve is configured such that therefrigerating capacity can only be increased by a factor of 1.4 at themaximum, in the fully-open state of the expansion valve, which makes itpossible to suppress generation of noise during start-up.

[0045] Further, due to the refrigerating capacity limited up to a scalefactor of 1.4, the noise immediately after start-up is made much smallerthan the prior art, as shown in FIG. 4. With the lapse of time, therefrigeration cycle becomes stable, causing the expansion valve 1 toenter the control region, so that the noise becomes equal in magnitudeto the prior art.

[0046] FIGS. 5(A) and 5(B) are diagrams for explaining tolerancedispersion, and FIG. 5(A) shows a case of a conventional expansionvalve, while FIG. 5(B) shows a case of the expansion valve according tothe present invention.

[0047] The expansion valve according to the present invention isrequired to make the maximum stroke of the shaft smaller than that ofthe conventional expansion valve. For example, in the case of 1.0-tontype expansion valve, the maximum stroke of the shaft is reduced fromthe conventional value of 0.8 mm to a value of 0.3 mm. Therefore,tolerance dispersion in the sizes of members determining the stroke hasa large influence on the valve, and therefore the dispersion is requiredto be made small. The expansion valve according to the present inventionsolves this problem by changing the stopper of the center disk 17 fromthe holder 22 to the lower housing 15 of the power element 13.

[0048] More specifically, in the conventional expansion valve, as shownin FIG. 5(A), the stroke S of the shaft 119 is from a position at whichthe center disk 117 is in contact with the top surface of the holder 122to the illustrated position assumed when the valve is fully closed.Further, P designates an amount of protrusion of the shaft 119 from thetop surface of the body block 102 when the valve is fully closed.Further, A designates a height from the stepped portion of the bodyblock 102, where the holder 122 is received, to the top surface of thebody block 102, B a height from the bottom surface of the holder 122lying on the stepped portion to a surface of the holder 122 with whichthe center disk 117 is brought into contact when the valve is fullyopened, and C a height from the surface of the center disk 117 withwhich the shaft 119 is in abutment to a surface of the center disk 117which is brought into contact with the holder 122 when the valve isfully opened.

[0049] By using the stepped portion receiving the holder 122 of the bodyblock 102 as the reference, an expression of (A+P)+C=B+S holds, and fromthis, the stroke S can be expressed as S=A+P+C−B. More specifically, thenumber of parameters determining the stroke S is four.

[0050] On the other hand, in the expansion valve 1 according to thepresent invention, as shown in FIG. 5(B), the stroke S of the shaft 19is from a position in which the center disk 17 is in abutment with theinner surface of the lower housing 15 to the illustrated positionassumed when the valve is fully closed. Now, if the top surface of thebody block 2 on which the power element 13 is mounted is used as thereference surface, and the thickness of the lower housing 15 isrepresented by t, the amount P of protrusion of the shaft 19 from thereference surface is expressed as P=t+S, so that the stroke S can beexpressed by S=P−t. Therefore, the number of parameters determining thestroke S becomes two, which means the number of dispersion-causingfactors is reduced to half. This makes it possible to make the tolerancedispersion smaller than the conventional expansion valve.

[0051] Particularly, when the holders 22, 122 are made of resin, sincethe resin is thermally expanded, the conventional expansion valvesuffers from dispersion of the parameter B caused by the refrigeranttemperature, which makes the value of the stroke S a function oftemperature. In contrast, in the present expansion valve, the parametersdetermining the stroke S do not contain the parameter B, which makes itpossible to further decrease the tolerance dispersion.

[0052]FIG. 6 is a longitudinal cross-sectional view showing anotherexample of the construction of the expansion valve. It should be notedthat in FIG. 6, the component elements identical to those shown in FIG.1 are designated by the same reference numerals, and a detaileddescription thereof is omitted.

[0053] An expansion valve la according to this embodiment is differentfrom the expansion valve 1 shown in FIG. 1 in which the center disk 17is guided by the inner wall surface of a vertical portion of the lowerhousing 15, in that the same is guided by the holder 22 of the shaft 19.

[0054] More specifically, the center disk 17 has a lower central portionprotruding downward, and this protruding portion is inserted in a holeformed in the top of a holder 22, whereby it is guided by the holder 22in a manner movable forward and backward along the axis of the shaft 19.This causes the center disk 17 to be positioned by the holder 22 on thesame axis as that of the shaft 19, which enables the center disk 17 tomove smoothly without being caught by the lower housing 15 when thecenter disk 17 is moved forward and backward by displacement of thediaphragm 16, providing stable flow rate characteristics.

[0055] The center disk 17 is configured such that a surface of theprotruding portion for abutment with the shaft 19 and a surface thereoffor abutment with the stopper of the lower housing 15 are both formed tobe flat, and a plurality of ventilation grooves is formed on the surfacefor abutment with the stopper in a radially extending manner, therebyallowing the refrigerant returned from the evaporator to enter thechamber below the diaphragm 16 via the ventilation grooves even when thevalve is in the state of the maximum valve lift in which the center disk17 is brought into contact with the lower housing 15.

[0056] Further, the expansion valve la according to this embodiment isconfigured such that an adjustment screw 12 a also plays the role of thespring receiver to thereby reduce the number of component parts.

[0057] As described heretofore, the expansion valve according to theinvention is configured such that the maximum valve lift provides a flowrate of refrigerant which is 1.0 to 1.4 times the flow ratecorresponding to the set tonnage. This limits the flow rate ofrefrigerant when the valve is fully open during start-up, therebyenabling reduction of noise generated when the refrigerant passesthrough the valve, and prevents an unnecessarily excessive amount ofrefrigerant from flowing, thereby enabling prevention of wasteful use ofdriving force.

[0058] Further, the stroke of the center disk of the power elementtoward the valve portion is restricted by the inner wall of the valveportion-side housing. This reduces the number of parameters determiningthe stroke, which makes it possible to make the number of factorscausing tolerance dispersion of the valve stroke smaller than the priorart.

[0059] Further, the valve seat is tapered, and the length of the taperedportion in an axial direction is made equal to or more than the lengthof stroke of the valve element. This makes it possible to prevent thevalve element from moving out of the tapered hole even when the helicalcompression spring urging the valve element is in an inclined state.

[0060] The foregoing is considered as illustrative only of theprinciples of the present invention. Further, since numerousmodifications and changes will readily occur to those skilled in theart, it is not desired to limit the invention to the exact constructionand applications shown and described, and accordingly, all suitablemodifications and equivalents may be regarded as falling within thescope of the invention in the appended claims and their equivalents.

What is claimed is:
 1. An expansion valve including a power element thatsenses pressure and temperature of refrigerant at an outlet of anevaporator and controls a valve lift of a valve portion, to therebycontrol a flow rate of refrigerant supplied to the evaporator,characterized in that a maximum value of the valve lift is set such thatthe flow rate is equal to 1.0 to 1.4 times a flow rate corresponding toa set tonnage.
 2. The expansion valve as claimed in claim 1, wherein thepower element causes a center disk for transmitting displacement of adiaphragm sensing the pressure and temperature of the refrigerant to avalve element of the valve portion via a shaft to be brought intoabutment with an inner wall of a housing toward the valve portion,thereby defining the maximum valve lift of the valve portion.
 3. Theexpansion valve as claimed in claim 2, wherein the center disk is guidedin a direction of displacement of the diaphragm, by a holder holding anend of the shaft on a side opposite to the valve portion.
 4. Theexpansion valve as claimed in claim 1, wherein the valve portioncomprises a valve seat, a valve element having a shape of a ball anddisposed in a manner opposed to the valve seat from an upstream side,and a spring for urging the valve element in a valve-closing direction,and wherein the valve seat is tapered such that an amount of tapering isequal to or larger than an amount of axial motion of the valve element.